barrels that are non chrome lined are typically more accurate because they break in faster and are slightly softer that chrome lined barrels, for the AR-15 it really doesnt matter if you get chromed or nonchromed, you are shooting non-corrosive ammo anyway, and you are not shooting the rifle full auto, so, civilian shooters like us donot need those features in our rifles, we clean them after shooting and even if you dont clean your rifles after cleaning they are not going to start rusting for a long, long time.
So dont let the chrome or non chrome influence your descision, The most accurate rifles out there are all non-chromed, they are all steel.
Hope this sets your troubled soul at rest